An excellent series of rebuttals against the allegations that certain Scholars performed tawassul (i.e. the innovated form of tawassul, not the legislated, legitimate form) has been posted in one of the forums in Arabic (here is original link), by "Abu Uthmaan". Inshaa'Allaah we will serialize this valuable material, since these types of doubts are frequently used by English-speakers too.

Before proceeding it should be made clear that:

In Islaam, worship (ibaadah) has been thoroughly explained, its definition, its pillars, its conditions, its types and forms. And as such there is a clear criterion in the matter of legitimate and illegitimate worship. With respect to "tawassul" which simply means to seek a means of nearness and approach, and then there is a legitimate form of tawassul, which is seeking nearness to Allaah through a) Calling upon Him by way of His Names and Attributes b) Doing sincere, righteous correct deeds and calling upon Him by way of them, and these righteous deeds include having faith in the Prophets and having love of them, all of which can be used as a means of nearness to Allaah c) the supplication of a righteous person. As for the innovated forms of tawassul, some of which are avenues leading to major shirk and some of which constitute major shirk (and these are covered in other articles), then they involve the physical bodies, or the "status", or the "honour", or the "right", of the Prophets or the Righteous, and this is not the place to go into this subject in detail, but will be addressed in other articles inshaa'Allaah, however it is important to realize some of them fall into the ruling of innovation (which open up the avenues that lead to shirk) and others are major shirk (giving worship to others besides Allaah).

Those who fall into these illegitimate forms of tawassul have their doubts and misconceptions and they often attempt to argue through certain narrations to justify their practices. There are also a restricted number of isolated sayings on this subject from some of the Scholars of the past which these people have misunderstood and misapplied, and that will be the subject of a separate set of articles.

Also an act of worship is established by a verse of the Qur'an or an authentic hadeeth of the Messenger (alayhis salaam), and as you will see, in most of these examples, these doubts are simply alleged actions of some of the Scholars - and that is not an independent proof for an act of worship - but that's discounting the fact that most of these alleged actions are reported through unacceptable inauthentic narrations.

Hamzah bin Yusuf as-Sahmee: (حدث عن من لم يره ، ومن مات قبل أن يولد), "He narrated from the one he never saw and from the one who died before he (Abu al-Hasan) was even born." (Su'aalaat as-Sahmee, p. 152). And he also said, (وسمعت الدارقطني وجماعة من المشايخ تكلموا في بن مقسم وكان أمره أبين من هذا ), "And I heard ad-Darqutnee and a group amongst the Mashaayikh (Scholars) [who] spoke about bin Muqsim and his affairs was more apparent than this." (p. 153).

From what has preceded, the narration is not authentic regarding Ibraaheem al-Harbee, and even if it was authentic, there is nothing within it that is evidence for the permissibility of tawassul or istighaathah (seeking rescue) by way of the physical essences (which is what the dispute is about).